Is the CPU chip overheating?
Is your video Captuer card overheathing?
I recommend that you check these things.
If one of these things are you have a overheating problem that is making this happen.
If you are overheating I would recommend that you check the fans.
i have recently installed the belkin dvd creator but after about 20 seconds of video capturing the computer switches intself of and restarts. Any ideas?